Damping device

ABSTRACT

A damping device, including: a wedge assembly having a wedge including a vertical surface and an inclined surface; a primary friction board disposed on the vertical surface; and a secondary friction board disposed on the inclined surface; and a damping spring assembly disposed underneath the wedge assembly. The wedge assembly has the following structure parameters: α=16-30°, and μ&lt;tgα&lt;μ+μ 1 , where α represents an included angle between a friction surface of the secondary friction board and a vertical plane, μ represents a friction coefficient of the primary friction board, and μ 1  represents a friction coefficient of the secondary friction board.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of International PatentApplication No. PCT/CN2010/079610 with an international filing date ofDec. 9, 2010, designating the United States, now pending, and furtherclaims priority benefits to Chinese Patent Application No.201010162237.1 filed Apr. 27, 2010. The contents of all of theaforementioned applications, including any intervening amendmentsthereto, are incorporated herein by reference. Inquiries from the publicto applicants or assignees concerning this document or the relatedapplications should be directed to: Matthias Scholl P. C., Attn.: Dr.Matthias Scholl Esq., 14781 Memorial Drive, Suite 1319, Houston, Tex.77079.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a damping device, and more particularly to adamping device for a wedge of a wheel truck of a railroad freight car.

2. Description of the Related Art

As a critical part of a freight car, a typical wheel truck of a railroadfreight car includes two side frame assemblies and a bolster assembly.Journal-box guides disposed on two ends of the side frame assembly arefixed on a front wheel pair and a rear wheel pair via roller bearingadapters and bearing assemblies, respectively. The bolster assembly hastwo ends, each of which is mounted in a central square hole of the sideframe assembly via a spring suspension device. The spring suspensiondevice is used to support the load of the bolster assembly and includesa bearing spring unit in the center and two frictional damping devicesfor a wedge on both sides.

The existing frictional damping device includes a wedge assembly and adamping spring assembly underneath the wedge assembly. A verticalprimary friction surface and an inclined secondary friction surface ofthe wedge assembly are attached to a column surface of the side frameassembly and an inclined surface of the bolster assembly, respectively.

The wheel truck of a railroad freight car, as described above, isadvantageous in its simple structure, uniform distribution of the load,low cost in production and maintenance. However, the connection betweenthe bolster assembly and the side frame assembly is loose and thediamond resistant rigidity is low, which cannot resist the violentshaking between the bolster assembly and the side frame assembly. Andwhen the wheel truck runs on a curved rail track, the attack anglebetween the wheel pairs and the rail enlarges, thereby resulting indamages on the wheel and the rail. Particularly, the wedge of the springsuspension device has a relative larger apex angle, that is, the angelbetween the secondary friction surface and a vertical plane is about35-70°. Thus, the diamond resistant rigidity is highly limited. When thebolster assembly moves downwards relative to the side frame assembly, avertical force component of a force from the inclined surface to thewedge is larger than a sum of vertical force components of the frictionproduced on the primary friction surface of the wedge and the frictionproduce on the secondary friction surface of the wedge, so that thewedge moves downwards, and the vertical distance between the bolsterassembly and the side frame assembly becomes smaller, thereby resultingin relative rotation between the bolster assembly and the side frameassembly, as well as diamond deformation. In such a condition, thecritical speed of the wheel truck is low, which limits the running speedand running performance of the freight car, and cannot meet therequirement of the speed-raising freight car.

To solve the above problems, the current speed-raising trains employs across supporting device between two side frame assembly or a springplank for improving the diamond resistant rigidity of the conventionalwheel truck. The problem is that, such a cross supporting device orspring plank has a complicated structure, heavy weight, and highproduction and maintenance costs. Thus, it is very significant toimprove the diamond resistant rigidity of the conventional wheel truckand the dynamic performance of the trains.

SUMMARY OF THE INVENTION

In view of the above-described problems, it is one objective of theinvention to provide a damping device that has a simple structure, lowproduction and maintenance costs, superb dynamic performance forcrossing curved tracks, and can meet high requirements of the diamondresistant rigidity for speed-raising trains.

To achieve the above objective, in accordance with one embodiment of theinvention, there is provided a damping device comprising a wedgeassembly and a damping spring assembly disposed underneath the wedgeassembly. The wedge assembly comprises a wedge, a primary friction boarddisposed on a vertical surface of the wedge, and a secondary frictionboard disposed on an inclined surface of the wedge. The wedge assemblyis provided with the following structure parameters: α=16-30°, andμ<tgα<μ+μ₁. Of them, α represents an included angle between a frictionsurface of the secondary friction board and a vertical plane; μrepresents a friction coefficient of the primary friction board; and μ₁represents a friction coefficient of the secondary friction board.

The included angle α of the wedge assembly is no more than 30°, which ismuch smaller than the conventional vertex angle of 35-70°, and meets therequirement that tgα<μ+μ₁. Thus, when the bolster assembly moves in ahorizontal direction relative to the side frame assembly, a downwardvertical force component of a force exerted on the wedge assembly fromthe inclined surface of the bolster remains smaller than a sum of upwardvertical force components of the friction produced on the primaryfriction board and the friction produced on the secondary frictionboard, so that the wedge assembly is prevented from moving downwards,relative rotation between the bolster assembly and the side frameassembly cannot occur, and a high diamond resistant rigidity ismaintained between the bolster assembly and the side frame assembly.Supposing that, the angle α is too small and approximates to thefriction angle of the primary friction board of the wedge assembly, thewedge assembly will be self-limited once the bolster assembly movesdownwards relative to the side frame assembly, thereby lowering thedynamic performance of the wheel truck. Therefore, the lower bound ofthe angle α of the wedge assembly is designed as 16°, and μ<tgα, to makesure that the wedge assembly moves freely during the vertical movementof the bolster assembly, and the wheel truck has a good dynamicperformance for crossing curved tracks.

In a class of this embodiment, a width of the wedge assembly isL=200-600 mm, which is at least 1.3 times longer than the width of theconventional wedge having a variable friction. The wedge having avariable friction herein means that a wedge is disposed on a dampingspring which is arranged in a square hole in a center of a side frame,the damping friction exerted on the wedge changes in proportional to thevariable vertical load exerted on the bolster assembly. Not only doesthe width design of the wedge assembly increase the length of the torquearm to resist the diamond deformation between the bolster assembly andthe side frame assembly; but also it increases attached area between theprimary friction board and the column surface of the side frameassembly, and between the secondary friction board and the inclinedsurface of the bolster assembly, so that the diamond resistant rigiditybetween the bolster assembly and the side frame assembly is furtherimproved.

In a class of this embodiment, a mechanical property of the dampingspring meets the following relation formula: K₁×ctgα=K×C/2μ, in which,K₁ represents a rigidity of the damping spring assembly; K represents atotal rigidity of a spring suspension device; C represents a relativefriction coefficient of the wheel truck and ranges from 0.05 to 0.15;and μ represents a friction coefficient of the primary friction board.As the rigidity K₁ of the damping spring assembly is inverselyproportional to ctgα of the wedge assembly, K₁ can be adjusted accordingto the value of angle α, thereby maintaining a suitable friction dampingforce, and preventing frictions from being too large during movements invertical and horizontal directions.

In a class of this embodiment, the secondary friction board is inconnection with the inclined surface of the wedge via a sphericalstructure comprising a convex surface and a corresponding concavesurface, which ensures good contact between the secondary friction boardand the inclined surface of the bolster, as well as good contact betweenthe primary friction board and the column surface. Thus, the reliabilityof the diamond resistance of the bolster assembly and the side frameassembly is highly improved, and at the same time, damages on theinclined surface of the bolster and the maintenance cost are largelydecreased.

Advantages of the invention are summarized hereinbelow:

First of all, the wedge assembly of the damping device not only assuresa free movement of the wedge assembly when the bolster moves in avertical direction, but also prevents the wedge assembly from movingwhen the bolster moves in a horizontal direction. Thus, the wheel truckhas an enough high diamond resistant rigidity and good dynamicperformance even without a crossed supporting device or a spring plank.Furthermore, the design of the width of the wedge assembly which is 1.3times longer than that of the conventional also improves the diamondresistant rigidity and the dynamic performance, thereby highly improvingthe critical speed of the freight car, the capacity of crossing curvedtracks, and the running performance. Finally, the wheel truck has asimple structure, light weight, and low production and maintenancecosts, which is applicable to the new railroad freight car having arunning speed of 120 km/h, and meets the requirements of the diamondresistant rigidity for the speed-raising trains.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described hereinbelow with reference to theaccompanying drawings, in which:

FIG. 1 is a stereogram of a damping device in accordance with oneembodiment of the invention;

FIG. 2 is a cross-sectional view of a damping device of FIG. 1;

FIG. 3 is a diagram of a damping device fitted with a bolster assemblyand a side frame assembly in accordance with one embodiment of theinvention;

FIG. 4 is a force balance diagram of a damping device as shown in FIG. 3during a movement of a bolster in horizontal direction; and

FIG. 5 is a force balance diagram of a damping device as shown in FIG. 3during a movement of a bolster downwards in vertical direction.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To further illustrate the invention, experiments detailing a dampingdevice are described below. It should be noted that the followingexamples are intended to describe and not to limit the invention.

As shown in FIGS. 1 and 2, a damping device for a wedge of a wheel truckof a railroad freight car comprises a wedge assembly 1 and a dampingspring assembly 2 disposed underneath the wedge assembly 1. The wedgeassembly 1 comprises a wedge 1 b comprising a vertical surface and aninclined surface, a primary friction board 1 a is disposed on thevertical surface, and a secondary friction board 1 c is disposed on theinclined surface. Structure parameters of the wedge assembly 1 are asfollows: L=200-260 mm, α=16-30°, and μ<tgα<μ+μ₁. Of them, L represents awidth of the wedge assembly 1; α represents an included angle between afriction surface of the secondary friction board 1 c and a verticalplane; μ represents a friction coefficient of the primary friction board1 a; and μ₁ represents a friction coefficient of the secondary frictionboard 1 c. According to the designing requirement of the value of theangle α, suitable materials of the primary friction board 1 a and thesecondary friction board 1 b can be selected and structures thereof canbe properly adjusted to make the values of μ and μ₁ meet theirrequirements.

As a supporting base, the wedge 1 b is made of steel or iron to meet therequired intensity and rigidity. Two secondary friction boards 1 c,being made of modified nylon materials, are symmetrically disposed onthe inclined surface of the wedge 1 b. The connection between thesecondary friction board 1 c and the inclined surface of the wedge 1 bis achieved by a spherical structure comprising a convex surface and acorresponding concave surface. As shown in FIG. 2, a convex sphericalsurface of the secondary friction board 1 c is received by acorresponding concave spherical surface of the inclined surface of thewedge 1 b. The structural design of the secondary friction board 1 c isadvantageous in that: on one hand, the convex spherical surface of thesecondary friction board 1 c matches well with the concave sphericalsurface of the inclined surface of the wedge 1 b, which assures the wellcontact between the secondary friction board 1 c and the inclinedsurface of the bolster, even when deviations occur in the apex angle αof the wedge assembly 1, the angel and the flatness of the inclinedsurface of the bolster. Thus, the wedge assembly 1 and the secondaryfriction board 1 c can maintain stable, and a large friction is producedto prevent the wedge assembly 1 from moving downwards when diamonddeformations occurs between the bolster unit and the side frameassembly, thereby effectively improve the diamond resistant rigidity ofthe wheel truck; on the other hand, the secondary friction board 1 cmade of modified nylon materials has a good abrasive resistance and highfriction coefficient, not only is the secondary friction board 1 chard-wearing, but also it alleviates the abrasion on the inclinedsurface of the bolster, thereby being convenient to fix and replace, andlowering the production cost. The primary fiction board 1 a is anintegrated friction board made of polymer materials that can be fixed ina slot on the vertical surface of the wedge 1 b via fasteners. Also, theconvex spherical surface of the secondary friction board 1 c and thematched concave spherical surface of the inclined surface of the wedge 1b assure the well contact between the primary friction board 1 a andcolumn surface of the side frame when deviation occurs in the apex angleα of the wedge assembly 1, the flatness of the inclined surface of thebolster, and the column surface of the side frame. Thus, a stabledamping property of the wedge assembly 1 is achieved.

As shown in FIG. 3, as a part of a spring suspension device, the dampingdevice is disposed between the side frame assembly 3 and the bolsterassembly 4. A lower part of the damping spring assembly 2 is disposed ona spring plank in the square hole of the side frame assembly 3. Theprimary friction board 1 a of the wedge assembly 1 is attached to thecolumn surface 3 a of the side frame; and the two secondary frictionboards 1 c of the wedge assembly 1 are attached to the inclined surface4 a of the bolster. Thus, the function of frictional damping is achievedin the running of the freight car.

As shown in FIG. 4, when the bolster assembly 4 moves in a horizontaldirection relative to the side frame assembly 3, the inclined surface 4a of the bolster assembly exerts a force N on the wedge assembly 1,then, a fiction F_(f) is produced between the inclined surface 4 a ofthe bolster assembly and the secondary friction board 1 c of the wedgeassembly 1, and a fiction F_(z) is produced between the column surface 3a of the side frame assembly and the primary friction board 1 a of thewedge assembly 1. It is known from FIG. 4 that a vertical forcecomponent of N is N_(y)=N×sin α, and a horizontal force component of Nis N_(z)=N×cos α. In addition, two upward frictions are exerted on thewedge assembly 1 on the primary friction board 1 a and the secondaryfriction board 1 c, respectively, in which, the friction produced on theprimary friction board 1 a is F_(z)=N_(z)×μ=N×cos α×μ, and the frictionproduced on the secondary friction board 1 c is F_(f)=N×μ₁. According tothe requirement that N_(y)<F_(z)+F_(f)×cos α, that is, N×sin α<N×cosα×μ+N×μ₁×cos α, a relation formula tgα<μ+μ₁ is acquired aftersimplification. Thus, the wedge assembly 1 is limited by the frictionsproduced on the primary friction board la and the secondary frictionboard 1 c from moving downwards, and an enough high diamond resistantrigidity between the bolster assembly 4 and the side frame assembly 3 isachieved.

As shown in FIG. 5, when the bolster assembly 4 moves downwards in avertical direction relative to the side frame assembly 3, the inclinedsurface 4 a of the bolster assembly exerts a force N on the wedgeassembly 1, then, a fiction F_(f) is produced between the inclinedsurface 4 a of the bolster assembly and the secondary friction board 1 cof the wedge assembly 1, and a fiction F_(z) is produced between thecolumn surface 3 a and the primary friction board 1 a of the wedgeassembly 1. It is known from FIG. 5 that a vertical force component of Nis N_(y)=N×sin α, and a horizontal force component of N is N_(z)=N×cosα. At this moment, two frictions are exerted on the wedge assembly 1, ofthem, the friction produced on the primary friction board 1 a F_(z) isupward, and the friction produced on the secondary friction board 1 cF_(f) is downward, and F_(z)=N_(z)×μ=N×cos α×μ. According to therequirement that F_(z)<N_(y), that is, N×cos α×μ<N×sin α, a relationformula μ<tgα is acquired after simplification. In such a way, the wedgeassembly 1 isn't limited by the friction produced on the primaryfriction board 1 a, and can move freely when the bolster assembly 4moves in vertical direction, thereby achieving a normal attenuationvibration of the wheel truck during the running of the freight car.

It is also known from FIG. 5 that the damping force exerted on the wedgeassembly 1 is mainly from the friction F_(z) produced on the primaryfriction board 1 a, and F_(z) is relevant to a bearing capacity P of thedamping spring assembly 2. The relation formula between F_(z) and P isF_(z)=P×ctgα×μ, in which, P=K₁×y. K₁ represents a rigidity of thedamping spring assembly 2; and y represents a flexibility of the dampingspring assembly 2. Thus, the formula above is converted asF_(z)=K₁×y×ctgα×μ. In order to remain a suitable damping force for thewedge assembly 1, a mechanical property of the damping spring assembly 2should meet the following requirement: K₁×ctgα=K×C/2μ, in which, Krepresents a total rigidity of the spring suspension device, and Crepresents a relative friction coefficient of the wheel truck and rangesfrom 0.05 to 0.15. As values of K and μ are determined by the designingrequirements, when angle α is decreased, ctgα decreases correspondingly,and the damping spring assembly 2 should be selected from materialshaving a lower rigidity K₁, to make the relative friction coefficient ofthe wheel truck remains in the range of 0.05-0.15, and to preventfrictions from being too large during movements in vertical andhorizontal direction.

The above damping device of the wheel truck of the freight car, has ahigh diamond resistant rigidity, high critical speed, and superb dynamicperformance for crossing curved tracks, even without adopting a crossedsupporting device or a spring plank. Thus, it is applicable to the newrailroad freight car having a running speed of 120 km/h, and meets therequirement for speed-raising.

While particular embodiments of the invention have been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention inits broader aspects, and therefore, the aim in the appended claims is tocover all such changes and modifications as fall within the true spiritand scope of the invention.

1. A damping device, comprising: a) a wedge assembly (1) comprising awedge (1 b) comprising a vertical surface and an inclined surface; aprimary friction board (1 a) disposed on the vertical surface; and asecondary friction board (1 c) disposed on the inclined surface; and b)a damping spring assembly (2) disposed underneath the wedge assembly(1); wherein in the wedge assembly (1), α=16-30°, and μ<tgα<μ+μ₁, whereα represents an included angle between a friction surface of thesecondary friction board (1 c) and a vertical plane, μ represents afriction coefficient of the primary friction board (1 a), and μ₁represents a friction coefficient of the secondary friction board (1 c).2. The damping device of claim 1, wherein a width of the wedge assembly(1) is L=200-260 mm
 3. The damping device of claim 1, wherein amechanical property of the damping spring assembly (2) meets thefollowing formula: K₁×ctgα=K×C/2μ, in which K₁ represents a rigidity ofthe damping spring assembly (2), K represents a total rigidity of aspring suspension device, and C represents a relative frictioncoefficient of the wheel truck of a railroad freight car and ranges from0.05 to 0.15.
 4. The damping device of claim 2, wherein a mechanicalproperty of the damping spring assembly (2) meets the following formula:K₁×ctgα=K×C/2μ, in which K₁ represents a rigidity of the damping springassembly (2), K represents a total rigidity of a spring suspensiondevice, and C represents a relative friction coefficient of the wheeltruck of a railroad freight car and ranges from 0.05 to 0.15.
 5. Thedamping device of claim 1, wherein the secondary friction board (1 c) isin connection with the inclined surface of the wedge (1 b) via aspherical structure comprising a convex surface and a correspondingconcave surface.
 6. The damping device of claim 2, wherein the secondaryfriction board (1 c) is in connection with the inclined surface of thewedge (1 b) via a spherical structure comprising a convex surface and acorresponding concave surface.
 7. The damping device of claim 3, whereinthe secondary friction board (1 c) is in connection with the inclinedsurface of the wedge (1 b) via a spherical structure comprising a convexsurface and a corresponding concave surface.
 8. The damping device ofclaim 4, wherein the secondary friction board (1 c) is in connectionwith the inclined surface of the wedge (1 b) via a spherical structurecomprising a convex surface and a corresponding concave surface.
 9. Thedamping device of claim 5, wherein two secondary friction boards (1 c)are symmetrically disposed on the inclined surface of the wedge (1 b).10. The damping device of claim 6, wherein two secondary friction boards(1 c) are symmetrically disposed on the inclined surface of the wedge (1b).
 11. The damping device of claim 7, wherein two secondary frictionboards (1 c) are symmetrically disposed on the inclined surface of thewedge (1 b).
 12. The damping device of claim 8, wherein two secondaryfriction boards (1 c) are symmetrically disposed on the inclined surfaceof the wedge (1 b).
 13. The damping device of claim 1, wherein the wedge(1 b) is made of steel or iron; the primary friction board (1 a) is madeof polymer materials; and the secondary friction board (1 c) is made ofmodified nylon materials.
 14. The damping device of claim 2, wherein thewedge (1 b) is made of steel or iron; the primary friction board (1 a)is made of polymer materials; and the secondary friction board (1 c) ismade of modified nylon materials.
 15. The damping device of claim 3,wherein the wedge (1 b) is made of steel or iron; the primary frictionboard (1 a) is made of polymer materials; and the secondary frictionboard (1 c) is made of modified nylon materials.
 16. The damping deviceof claim 4, wherein the wedge (1 b) is made of steel or iron; theprimary friction board (1 a) is made of polymer materials; and thesecondary friction board (1 c) is made of modified nylon materials. 17.The damping device of claim 5, wherein the wedge (1 b) is made of steelor iron; the primary friction board (1 a) is made of polymer materials;and the secondary friction board (1 c) is made of modified nylonmaterials.
 18. The damping device of claim 6, wherein the wedge (1 b) ismade of steel or iron; the primary friction board (1 a) is made ofpolymer materials; and the secondary friction board (1 c) is made ofmodified nylon materials.